The benefits of having engines generating thrust vectoring or vectored thrust are well known. In recent years systems which allow obtaining and controlling the thrust vector of engines have been developed on the basis of essentially two actuation types: either through selectively diverting the engine exhaust gases and/or the air from the bypass fan by means of directional mechanical elements within the nozzles (see for example ES2010586), or through the variable exhaust gas area without modifying the thrust vector angle of the engines. All these mechanisms to a greater or lesser extent add complexity both to the configuration of the nozzles and to the control systems thereof, which leads to rejecting their use in many of the new aircraft models given that the ratio between the benefits of using them and the associated problems and expenses involved with the fact that they are located in an element that is as complex and of vital security in an aircraft, such as its propulsion systems, is not positive.
As described in document U.S. Pat. No. 6,938,408 B2, thrust vectoring technology has obtained very satisfactory results in military aeronautics, from the use demonstrated in military airplanes for low speed flight conditions or with high angles of attack, as well as its testing at high altitudes and mid-high speeds for the purpose of reducing the drag in cruise flight. Defining the stability of an airplane as the forces and moments generated in order to recover the equilibrium position when it is out of said position, the greater the stability of an aircraft, the less the maneuverability thereof, i.e. the less the capacity of the control surfaces to take the apparatus out of equilibrium, will be less. It is for this reason that systems adding controllability to the airplane, such as the vectored thrust of the engines, have been used above all in military aviation in which its applicability has no room for doubts given its configuration in which maneuverability or controllability of the aircraft is top priority. However this same system, as occurs with the rest of the aerodynamic and control surfaces of the airplane, which can contribute to the aircraft diverting from its equilibrium point, can be applied in an identical manner to the opposite fact, i.e. it can contribute to the static and dynamic longitudinal stability of the aircraft.
The use of thrust vectoring systems in commercial aviation is also understood from the aircraft energy efficiency point of view. It is known that in order for an aircraft to have longitudinal stability its center of gravity (CG) must be at a certain distance for each flight condition with respect to the aerodynamic center of pressure (CP). Airplanes are designed such that the diving moment, caused by the fact that the CG is located in front of the CP, is counteracted with the moment caused by the horizontal tail stabilizer. If it is possible to contribute to the stability of the aircraft through being able to guide the exhaust gases, airplanes can be designed in which the area of the tail assembly is less and works with smaller angles of attack, therefore creating less aerodynamic drag. Reducing the aerodynamic drag and the structural weight implies less propulsion energy waste and consequently improved energy efficiency.
Several studies carried out emphasize the improvement in all flight conditions by optimizing the thrust vector angle. One of the main considerations when designing an airplane is the tilt angle of the engines with respect to the horizontal of the fuselage. Optimal tilt depends on the features of the airplane as well as on the flight conditions. From the point of view of the effects occurring on the wing, a positive thrust angle contributes to reducing the lift requirements of the wing, although it implies a slight reduction in the horizontal thrust component. The initiative for developing a variable thrust system makes sense with the fact that in each flight condition the optimal thrust angle varies. The controllability of this variable in flight aids in reducing the speed and the distance during takeoff, in reaching a higher altitude with the same propulsion level in the climb phase, minimum propulsion in cruise conditions, a better gliding range in the descent and reducing the final approach speed and consequently the landing distance.
The benefits of using thrust vectoring are likewise described in documents known in the art seeking a viable solution for use, which contrasts with its subsequent applicability in real aircraft designs. The purpose of the present invention is not only to develop a system providing thrust vectoring in the aircraft, but that the system can also be applied. The main problem considered by the patented systems until now is the complexity added by their use in flight. Thus, the large number of moving elements which these systems provide to the nozzles of the engines means that their use entails an excessive maintenance expense to ensure proper operation of the system. Other known systems add great complexity to the flight control systems, which means that the time used in their optimal operational capacity does not result in the improvement of the overall behavior of the aircraft in which they intend to influence, but they are not determining factors of said behavior.
The present invention offers a solution to the previously mentioned problems.